docs: def run_get_clusters_from_file(self, clusters_infile, all_ref_seqs, rename_dict=None):
          '''Instead of running cdhit, gets the clusters info from the input file.'''
          if rename_dict is None:
              rename_dict = {}
  
          # check that every sequence in the clusters file can be
          # found in the fasta file
          seq_reader = pyfastaq.sequences.file_reader(self.infile)
          names_list_from_fasta_file = [seq.id for seq in seq_reader]
          names_set_from_fasta_file = set(names_list_from_fasta_file)
  
          clusters = self._load_user_clusters_file(clusters_infile, all_ref_seqs, rename_dict=rename_dict)
  
          if len(names_set_from_fasta_file) != len(names_list_from_fasta_file):
              raise Error('At least one duplicate name in fasta file ' + self.infile + '. Cannot continue')
  
          names_from_clusters_file = set()
          for new_names in clusters.values():
              names_from_clusters_file.update(new_names)
  
          if not names_set_from_fasta_file.issubset(names_from_clusters_file):
              raise Error('Some names in fasta file "' + self.infile + '" not given in cluster file. Cannot continue')
  
          return clusters